1. Field of the Invention
The present invention relates to, for example, an image forming apparatus for forming an electrostatic latent image on an image bearing body by the electrophotographic method and visualizes the electrostatic latent image with developer stored in a developing apparatus, and more particularly to an image forming apparatus having a developer amount detecting device provided with residual developer amount detecting means capable of serially detecting the residual amount of developer stored in a developer container as well as a cartridge that is insertable in the image forming apparatus main body, that is, a process cartridge, and a developing apparatus constituted as a cartridge.
Here, for example, an image forming apparatus includes an electrophotographic copying machine, an electrophotographic printer (for example, an LED printer, a laser beam printer and the like), an electrophotographic facsimile apparatus and so on.
In addition, here, a process cartridge also refers to a cartridge which is integrally composed of at least one of charging means, developing means and cleaning means, and an electrophotosensitive body, and is made detachably attachable to an electrophotographic image forming apparatus main body, or it refers to a cartridge that is integrally composed of at least developing means and an electrophotosensitive body, and is made detachably attachable to an electrophotographic image forming apparatus main body.
2. Related Background Art
In a conventional image forming apparatus using an electrophotographic image forming process, the process cartridge method is adopted, in which the cartridge is integrally composed of an electrophotographic sensitive body and process means which processes the electrophotosensitive body and makes the cartridge detachably attachable to an electrophotographic image forming apparatus main body. In accordance with the process cartridge method, since the maintenance of the apparatus can be conducted by a user in person and not by a serviceman, the operability is considerably improved. Hence, the process cartridge method is widely used in electrophotographic image forming apparatuses.
In an electrophotographic image forming apparatus with a process cartridge method, although an image can be formed again by replacing a cartridge when the developer is exhausted, the replacement of a cartridge should be performed by a user in person, and therefore, means for warning a user that the developer is exhausted, i.e., a developer amount detecting device, is required.
As a developer amount detecting device, a residual developer amount detecting means which can detect a residual developer amount level is located in a cartridge or an image forming apparatus main body in order to make it possible to find at any time how much developer is left to form images in the cartridge.
There is a electrostatic capacitance detecting method as one method of this residual developer amount detecting means. This is the method for detecting a residual developer amount utilizing the change of a current induced in an antenna in accordance with the developer amount existing between an electrode and the antenna when the antenna for detecting the residual developer amount is disposed in a developer container and an AC voltage is applied to the electrode located at a predetermined position.
For example, there is the flat antenna method as one of using the electrostatic capacitance detecting method. A flat antenna has a pair of conductor patterns 22, 23 formed in a predetermined interval on a substrate 21, and is, for example, disposed on a side of a developer container and on which the antenna contacts the developer, as the amount of the developer in the developer container decreases, so as to decrease the contacting area between the developer and the flat antenna 20.
The electrostatic capacity varies as the contacting area of the conductor pattern surface and the developer changes due to the consumption of the developer, thereby making it possible to interrelate the residual developer amount in the container with the electrostatic capacity of the flat antenna, and to find the residual developer amount in the container at any time by measuring the electrostatic capacity of the flat antenna.
By applying a constant alternate current bias on one of the pair of conductor portions 22, 23, the electrostatic capacity of the flat antenna 20 can be found from current flowing to the other conductor part at that time.
In addition, as another example using the electrostatic capacity detecting method, there is the plate antenna method configured with a metal plate (a plate antenna) provided in parallel with a developing roller in what is called the jumping developing method for developing a latent image on a photosensitive body by applying an alternating bias on the developing roller that is a developer carrying body disposed in a developer container.
This method utilizes the change of an electrostatic capacitance between the plate antenna and the developing roller depending on the amount of insulating developer existing between them. The electrostatic capacitance is large if a cavity between the plate antenna and the developing roller is filled with the developer, and air in the cavity increases as the developer decreases so that the electrostatic capacitance gets smaller. Therefore, the developer amount can be detected by relating the electrostatic capacitance with the developer amount between the plate antenna and the developing roller in advance.
As a measuring method of the electrostatic capacitance, the electrostatic capacitance can be found by measuring a current flowing to the plate antenna when an alternating bias, which is a developing bias, is applied on the developing roller. That is, this residual developer amount detecting method can detect a residual developer amount at the time of image formation when a developing bias is applied on the developing roller.
By providing the above described residual developer amount detecting means in a developer containing portion, i.e., a developer container, a residual developer amount capable of serving an image formation function can be found at any time.
In addition, as residual developer amount detecting means, there is the torque detection method in which a developer agitating means is provided in a developer container, for detecting a residual developer amount utilizing the change of load applied on developer agitating means depending on a residual developer amount.
By using such a serial residual developer amount detecting method, a user can be informed of how many more images can be formed until a replacement of a process cartridge, a developing device or the like formed into cartridge, a supplement of developer into the cartridge, or the like becomes necessary.
However, in any of the serial residual developer amount detecting methods, although it is possible to find at any time how much developer capable of serving an image formation is left, sufficient accuracy of detection has not been attained due to a limit in measurement resolution, a measurement error and the like, and the accuracy of detection concerning the printable number of sheets from the present onward is not yet satisfactory.
Thus, means is expected to be developed that informs the user precisely how many more images can be formed until a replacement of a process cartridge, a developing device or the like formed into cartridge, a supplement of developer into the cartridge, or the like becomes necessary.
The present invention relates to a further improvement of an image forming apparatus and a cartridge detachably attachable to the image forming apparatus as described above.
The present invention has been made in view of the above problems, and therefore has an object to provide an image forming apparatus capable of accurately detecting the remaining printable number of sheets, and to provide a cartridge detachably attachable to the image forming apparatus.
Another object of the present invention is to provide an image forming apparatus capable of accurately indicating the remaining printable number of sheets, and to provide a cartridge detachably attachable to the image forming apparatus.
Still another object of the present invention is to provide an image forming apparatus comprising:
a developer container for containing a developer;
developer amount detecting means for detecting an amount of the developer contained in the developer container;
a pixel number counter for counting the number of pixels required for forming an image;
a sheet number counter for counting the number of sheets of a recording material on which an image is formed; and
calculating means for calculating the printable number of sheets from the present onward using the developer amount detected by the detecting means, the number of pixels counted by the pixel number counter and the number of sheets counted by the sheet number counter.
Yet still another object of the present invention is to provide a cartridge comprising:
a developer container; and
a memory for memorizing a developer amount detected by a detecting means for detecting an amount of a developer contained in the developer container, the number of pixels counted by a pixel number counter, and the number of sheets counted by a sheet number counter.
Further objects of the present invention will become apparent by reading the following detailed description with reference to the attached drawings.